As the development of nanoscale mechanical, electrical, chemical and biological devices and systems increases, new processes and materials are needed to fabricate nanoscale devices and components. This is especially true as the scale of these structures decreases into the nanometer length scale wherein dimensions may extend from a few nanometers to tens of nanometers. There is a particular need for materials and methods that are able to duplicate nanoscale patterns over large areas accurately and with a high degree of reproducibility and process latitude. Block copolymer materials are useful in nanofabrication because they self-assemble into distinct domains with dimensions from a few nanometers to the tens of nanometers.
However, existing methods of directed self assembly using block copolymer materials suffer from limitations. For example, defect formation remains an issue, particularly if there is a slight mismatch between the natural length scales of the polymer blocks and the guiding features in chemical or graphoepitaxy.
Further, it is usually desirable for the blocks within block copolymers to have narrow distributions in molar mass. Such distributions can be achieved by using anionic polymerization (see R. P. Quirk et al. in “Thermoplastic Elastomers,” Hansen, Munich, Germany, pp. 74-78, (1996)) or +living free radical polymerization methods such as atom transfer radical polymerization (ATRP) (see, for example, T. E. Patten et al., Adv. Mater. Vol. 10, p. 901, 1998) or stable free radical polymerization (SFRP) using TEMPO (see, for example, N. A. Listigovers et al. Macromolecules Vol. 29, p. 8992, 1996) or similar nitroxide based initiators. However, these polymerization methods may tend to produce polymers containing various levels of metal ion contaminants such as aluminum, calcium, chromium, copper, iron, magnesium, manganese, nickel, potassium, sodium, zinc, tin, cadmium, cobalt, germanium, lead, lithium, silver, or titanium. Such contaminants may be undesirable in semiconductor manufacturing.
Moreover, as with any industrial process, it is desirable to allow as much process latitude as possible so that the influence of difficult-to-control process variables can be minimized.
What is needed therefore, are methods and materials for producing patterns via directed self assembly that offer low defect formation, low metal ion contamination and improved process latitude. One or all of these features may be obtained using the methods and materials disclosed and claimed herein.